Causes of Male Infertility

Understanding Male Factor Infertility and Low Sperm Count

What Causes Male Infertility?

Male infertility can result from a variety of factors that affect sperm production, sperm quality, or the ability to successfully deliver sperm during intercourse. In some cases, men experience no obvious symptoms, making fertility testing an important step in identifying potential underlying issues.

The most common causes of male infertility include:

Low sperm count
Poor sperm motility (movement)
Abnormal sperm morphology (shape)
Varicocele (enlarged veins around the testicle)
Hormonal imbalances
Genetic conditions
Infections
Lifestyle factors such as smoking, obesity, excessive alcohol consumption, and drug use
Exposure to environmental toxins
Previous surgery, injury, or medical treatments

It is also important to note that erectile dysfunction (ED) does not directly damage sperm or cause biological infertility. However, it can make natural conception more challenging because it may affect a man's ability to achieve or maintain an erection and successfully deliver sperm into the female reproductive tract during intercourse.

Male factor infertility contributes to around half of all fertility difficulties experienced by couples, making male fertility testing a crucial first step when conception is taking longer than expected.

What Is Male Factor Infertility?

Male factor infertility refers to any issue affecting sperm production, sperm function, or sperm delivery that reduces the chances of natural conception.

Male factor infertility is common and is estimated to contribute to around 50% of fertility difficulties experienced by couples. As a result, assessing male fertility is an important part of understanding why conception may not be occurring as expected.

Many causes of male infertility do not produce noticeable symptoms. As a result, fertility testing is often the most effective way to assess sperm health and identify any underlying issues that may affect conception.

This is why comprehensive fertility testing is often the most effective way to identify underlying problems early.

Low Sperm Count Causes

FIND OUT WHY IT MATTERS

A common form of male factor infertility is a low sperm count, medically known as oligospermia.

A healthy sperm count increases the likelihood that sperm will successfully reach and fertilise an egg. When sperm numbers fall below normal levels, conception can become more challenging.

Varicocele

A varicocele is an enlargement of the veins within the scrotum and is one of the most commonly identified and treatable causes of male infertility.

The condition can lead to increased testicular temperature and changes in the local environment of the testes, which may negatively affect sperm production, motility, and overall sperm quality. More recent evidence, including large systematic reviews and meta-analyses, has also shown that varicoceles are associated with higher levels of sperm DNA fragmentation, which may impact fertility potential and the ability of sperm to successfully fertilise an egg (Palani et al., 2026).

Research suggests that treating a clinically significant varicocele may improve semen parameters and reduce sperm DNA damage in appropriately selected patients, supporting its role as a potentially correctable factor in male infertility (Palani et al., 2026).

Common symptoms include:

Dull aching discomfort
Visible enlarged or twisted veins within the scrotum
A feeling of heaviness in the testicles
Reduced sperm quality identified on semen analysis

However, many men with a varicocele experience no symptoms at all, and the condition is often only identified during fertility investigations.

Hormonal Imbalances

Sperm production is regulated by a complex hormonal system involving the brain (hypothalamus), pituitary gland, and testes. This communication network controls testosterone production and supports the development and maturation of sperm.

Endocrine disorders (endocrinopathies) can disrupt this balance and are recognised as an important cause of male infertility. Changes in key reproductive hormones can impair sperm production and function, and in some cases may also affect sexual function and overall reproductive health (Sengupta et al., 2021).

Hormonal causes of male infertility may involve:

Reduced testosterone production
Abnormal follicle-stimulating hormone (FSH) levels
Abnormal luteinising hormone (LH) levels
Raised prolactin levels (hyperprolactinaemia)
Thyroid dysfunction (overactive or underactive thyroid)

These hormonal imbalances can interfere with normal sperm development and may contribute to reduced sperm count or impaired sperm quality.

Hormonal causes of infertility can often be identified through targeted blood testing. In many cases, once the underlying endocrine disorder is diagnosed, treatment can help restore hormonal balance and improve fertility outcomes.

Genetic Factors

Genetic abnormalities are recognized as a significant cause of male infertility and can affect sperm production, sperm transport, and overall reproductive function (Plaseska-Karanfilska et al., 2012). These disorders may result from chromosomal abnormalities or specific gene mutations.

Common genetic causes include:

Klinefelter syndrome (47,XXY), which is the most common chromosomal abnormality associated with male infertility (Plaseska-Karanfilska et al., 2012).
Y chromosome microdeletions, particularly within the azoospermia factor (AZF) regions that are essential for normal spermatogenesis (Plaseska-Karanfilska et al., 2012).
Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which are frequently linked to congenital bilateral absence of the vas deferens and obstructive infertility (Plaseska-Karanfilska et al., 2012).
Structural or numerical chromosomal abnormalities that can impair sperm development and reduce fertility potential (Plaseska-Karanfilska et al., 2012).

Genetic testing is recommended for men with severe oligozoospermia or azoospermia because identifying an underlying genetic cause can support diagnosis, guide treatment decisions, and facilitate genetic counseling (Plaseska-Karanfilska et al., 2012).

Infections

Infections can interfere with fertility in several ways.

They may:

Damage sperm-producing tissue
Cause inflammation
Create blockages within the reproductive tract
Affect sperm movement and function
Potential causes include:
Previous sexually transmitted infections
Epididymitis
Orchitis
Prostatitis
Other inflammatory conditions

Advanced semen testing may identify signs of infection or elevated white blood cells within a sample.

Can Fever Affect Male Fertility?

Recent illness accompanied by a fever may temporarily affect sperm quality. Research has shown that elevated body temperature can reduce sperm concentration, motility, and morphology during key stages of sperm development. The impact may be more noticeable after prolonged or repeated episodes of fever, and changes to semen parameters can persist for several weeks or months while new sperm are produced. Because sperm development takes approximately 70–90 days, a recent fever or significant illness may sometimes help explain temporary changes seen in a semen analysis. In many cases, sperm quality improves over time once the underlying illness has resolved (Carlsen et al., 2003).

Previous Surgery, Injury or Medical Treatment

Certain medical treatments can affect fertility.

Examples include:

Testicular surgery
Hernia repair
Chemotherapy
Radiotherapy
Vasectomy
Significant testicular trauma

In some cases, fertility may recover naturally over time. In others, specialist intervention may be required.

Lifestyle Factors Affecting Sperm Quality

Many low sperm count causes relate to modifiable lifestyle factors.

Smoking

Smoking has been associated with reduced sperm concentration, poorer motility, and increased DNA damage (Aboulmaouahib et al., 2018).

Excessive Alcohol

Heavy alcohol consumption can:

Lower testosterone levels
Affect hormone balance
Reduce sperm production

Obesity

Excess body weight can alter hormone levels and increase oxidative stress, both of which may negatively affect fertility (Aboulmaouahib et al., 2018).

Heat Exposure

The testes function best at temperatures slightly below normal body temperature.

Regular exposure to heat may affect sperm production, including:

Frequent hot tubs or saunas
Prolonged laptop use on the lap
Certain occupational exposures
Extended periods of sitting

While occasional heat exposure is unlikely to cause significant fertility problems, chronic exposure may contribute to reduced sperm quality (Hoang-Thi et al., 2022).

Causes of Poor Sperm Motility

Even when sperm counts are normal, sperm must be able to move effectively to reach and fertilise an egg. Poor sperm motility, also known as asthenozoospermia, is a common factor in male infertility and can reduce the likelihood of natural conception.

Poor motility may result from:

Varicocele
Infection or inflammation of the reproductive tract
Oxidative stress
Lifestyle factors such as smoking, obesity, and excessive alcohol consumption
Genetic abnormalities
Antisperm antibodies
Exposure to environmental toxins
Hormonal imbalances

In some cases, abnormalities in seminal fluid composition may also be associated with reduced sperm motility. Fructose is a naturally occurring sugar produced primarily by the seminal vesicles and forms an important energy source for sperm, supporting their movement and function within the reproductive tract (Echevarría et al., 2024).

Recent research has highlighted the biological role of fructose in male reproductive health, particularly its contribution to sperm energy metabolism and overall semen function. When seminal fructose levels are altered, it may reflect changes in the function of the seminal vesicles or other accessory glands involved in semen production. These changes can be associated with variations in semen quality, including reduced sperm motility and lower seminal volume (Echevarría et al., 2024).

Comprehensive semen analysis can help assess sperm movement and overall semen health. Where abnormalities are identified, further investigations may be recommended to understand the underlying cause and guide appropriate treatment options.

Causes of Abnormal Sperm Morphology

Sperm morphology refers to the size, shape, and structural appearance of sperm. It is one of the key parameters assessed during semen analysis and provides information about sperm development and potential function.

Abnormal sperm morphology (teratozoospermia) refers to an increased proportion of sperm with atypical features, including abnormalities affecting the sperm head, midpiece, or tail. These structural changes may influence sperm function, including movement, interaction with the egg, and fertilisation potential.

Abnormal morphology may be associated with several factors, including:

Varicocele (enlarged veins around the testicle), which may alter the testicular environment and affect sperm development
Oxidative stress, which can contribute to sperm cellular damage
Lifestyle factors such as smoking, obesity, and excessive alcohol consumption
Environmental exposures and toxins
Increased testicular temperature or prolonged heat exposure
Genetic factors affecting sperm production and development
Infections or inflammation affecting the reproductive tract

However, sperm morphology should be interpreted alongside other semen parameters, including sperm concentration and motility, rather than as an isolated predictor of fertility. Reduced morphology alone does not necessarily indicate an inability to conceive, as many men with abnormal morphology may still achieve pregnancy depending on the wider clinical context and other fertility factors (Pelzman & Sandlow, 2024).

When significant abnormalities are identified, further investigations may be recommended to explore potential contributing factors and support personalised fertility management decisions (Pelzman & Sandlow, 2024).

Why Male Fertility Testing Matters

FIND OUT MORE

Male fertility factors contribute significantly to many cases of infertility, and importantly, many underlying causes can be identified, treated, or managed once they are properly investigated.

Despite this, male fertility concerns are often overlooked, with investigations sometimes focusing primarily on the female partner. Current guidance increasingly emphasises the importance of assessing both partners from the beginning of the fertility journey. Early male fertility assessment allows couples to better understand their options, make informed decisions, and potentially avoid unnecessary delays or treatments.

A semen analysis remains the cornerstone of male fertility assessment, providing valuable information about key aspects of sperm health, including:

Sperm count – the total number of sperm present within the sample
Sperm concentration – the number of sperm per millilitre of semen
Sperm motility – how effectively sperm move, including their ability to swim forward
Sperm morphology – the size and shape of sperm cells
Semen volume – the amount of semen produced during ejaculation
Semen pH – an indicator of the health and function of the reproductive tract
Signs of infection or inflammation – including the presence of white blood cells
MAR (Mixed Antiglobulin Reaction) Binding Test – used to detect antisperm antibodies that may interfere with sperm movement and fertilisation
Sperm vitality (where required) – assesses the percentage of live sperm present when motility is reduced, helping to distinguish between non-moving live sperm and dead sperm

At Fertility Solutions, we also count with advanced male fertility investigations which are available to provide a more detailed assessment, helping identify potential factors that may affect fertility and support personalised treatment decisions.

When Should You Seek Help?

You should consider a fertility assessment if:

You have been trying to conceive for 12 months without success
You have been trying to conceive for 6 months, and your partner with ovaries is over 35 years of age.
You have a history of testicular problems
You have undergone chemotherapy or fertility-impacting treatment
You have previously received abnormal semen analysis results

Early investigation can often identify problems sooner and create a clearer pathway towards treatment or natural conception.

FAQs

In many cases, a low sperm count can be improved depending on the underlying cause. The first step is identifying why sperm production or quality may be affected through appropriate fertility testing.

There are many potential causes of low sperm count, including infections, hormonal imbalances, varicocele, genetic factors, recent illness or fever, and lifestyle factors such as smoking, excessive alcohol intake, obesity, and exposure to environmental toxins.

Lifestyle changes may help improve sperm quality where these factors are contributing. In some cases, treating an underlying condition can also improve sperm parameters. For example, men with a clinically significant varicocele may benefit from treatment, and men with certain hormonal abnormalities may be suitable for medical management.

However, not all causes are reversible. Some genetic conditions or severe abnormalities in sperm production may have limited treatment options. A detailed semen analysis and, where appropriate, additional investigations can help identify the cause and guide the most suitable next steps.

Not always. Many causes of male infertility are treatable or manageable, and fertility outcomes can improve when the underlying cause is identified and appropriately addressed.

Factors such as varicocele, hormonal imbalances, infections, and lifestyle-related factors may be treatable and can sometimes lead to improvements in sperm quality.

However, some conditions, including certain genetic causes or severe problems affecting sperm production, may have a more significant impact on fertility potential. This is why early assessment is important, as it helps identify the cause and provides a clearer understanding of available options.

Male infertility can have many different causes, and often more than one factor may contribute.

A varicocele (enlarged veins around the testicle) is one of the most commonly identified and potentially treatable causes of male infertility. Other common contributors include:

Low sperm count
Reduced sperm motility (movement)
Abnormal sperm morphology (shape)
Hormonal imbalances
Genetic conditions
Infections or inflammation
Lifestyle factors such as smoking, obesity, and excessive alcohol consumption

A semen analysis is usually the first step in assessing male fertility and can help identify whether sperm-related factors may be affecting conception.

If you have not had any previous fertility testing, a semen analysis is usually the first recommended investigation.

A semen analysis provides important information about sperm health, including:

Sperm count – the total number of sperm present within the sample
Sperm concentration – the number of sperm per millilitre of semen
Sperm motility – how effectively sperm move, including their ability to swim forward
Sperm morphology – the size and shape of sperm cells
Semen volume – the amount of semen produced during ejaculation
Semen pH – an indicator of the health and function of the reproductive tract
Signs of infection or inflammation – including the presence of white blood cells
MAR (Mixed Antiglobulin Reaction) Binding Test – used to detect antisperm antibodies that may interfere with sperm movement and fertilisation
Sperm vitality (where required) – assesses the percentage of live sperm present when motility is reduced, helping to distinguish between non-moving live sperm and dead sperm

If abnormalities are identified, further investigations may be recommended to understand the underlying cause. These may include hormone testing, infection screening, genetic testing, or advanced sperm assessments depending on the individual situation.

Poor sperm motility (known as asthenozoospermia) means sperm are not moving effectively enough to reach and fertilise an egg.

Possible causes include:

Varicocele
Infections or inflammation
Hormonal imbalances
Genetic factors
Oxidative stress
Smoking and excessive alcohol consumption
Obesity
Exposure to environmental toxins
Antisperm antibodies

Changes in semen composition may also affect sperm movement. Advanced semen testing can provide further information when routine analysis does not fully explain reduced fertility potential.

Yes, lifestyle factors can influence sperm health. Since sperm production takes approximately 70–90 days, positive changes may take several months before improvements are seen.

Factors that may support healthier sperm production include:

Stopping smoking
Maintaining a healthy weight
Reducing excessive alcohol intake
Managing stress
Exercising regularly
Avoiding excessive heat exposure to the testes
Maintaining a balanced diet

Lifestyle changes may improve sperm parameters when these factors are contributing to reduced fertility, although

A fertility assessment may be recommended if:

You have been trying to conceive for 12 months without success
You have been trying to conceive for 6 months and your partner is over 35 years old
You have a history of testicular problems
You have previously had abnormal semen results
You have undergone chemotherapy, radiotherapy, or other treatments that may affect fertility
You have concerns about sperm health or fertility potential

Early testing can help identify potential causes sooner and provide a clearer pathway for management or treatment.

Take the First Step Towards Answers

BOOK NOW

Understanding the causes of male infertility is the first step towards improving your chances of conception. Whether fertility challenges stem from low sperm count, poor sperm quality, hormonal imbalance, or an underlying medical condition, early diagnosis provides the best opportunity to identify effective solutions.

At Fertility Solutions, we specialise in comprehensive male fertility assessment, combining expert interpretation with advanced diagnostic testing to provide clear answers and personalised recommendations.

References

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Echeverría CE, Oyarzún VI, López-Cortés A, Cancino J, Sotomayor PC, Goncalves MD, Godoy AS. Biological role of fructose in the male reproductive system: Potential implications for prostate cancer. Prostate. 2024 Jan;84(1):8-24. doi: 10.1002/pros.24631. Epub 2023 Oct 27. PMID: 37888416; PMCID: PMC10872645.

Palani A, Çayan S, Cannarella R, Saleh R, Altay B, Kadihasanoglu M, Harraz A, Dimitriadis F, Ceyhan E, Rezano A, Zwamel AH, Ibrahim W, Benabbou A, Margiana R, Gnoneye E, Rabin MMM, Omirinde J, Esmaeili V, Zini A, Arafa M, Elbardisi H, Toprak T, Dursun M, Khalafalla K, Salvio G, Chung E, Crafa A, Shah R, Agarwal A. Sperm DNA Fragmentation in Men with Varicocele: A Systematic Review and Meta-Analysis. World J Mens Health. 2026 Apr;44(2):268-289. doi: 10.5534/wjmh.250025. Epub 2025 Jun 19. PMID: 40583011; PMCID: PMC13036259.

Sengupta P, Dutta S, Karkada IR, Chinni SV. Endocrinopathies and Male Infertility. Life (Basel). 2021 Dec 22;12(1):10. doi: 10.3390/life12010010. PMID: 35054403; PMCID: PMC8779600.

Plaseska-Karanfilska D, Noveski P, Plaseski T, Maleva I, Madjunkova S, Moneva Z. Genetic causes of male infertility. Balkan J Med Genet. 2012 Dec;15(Suppl):31-4. doi: 10.2478/v10034-012-0015-x. PMID: 24052740; PMCID: PMC3776680.

Pelzman DL, Sandlow JI. Sperm morphology: Evaluating its clinical relevance in contemporary fertility practice. Reprod Med Biol. 2024;23(1):e12594. doi:10.1002/rmb2.12594.

Palani A, Çayan S, Cannarella R, Saleh R, Altay B, Kadihasanoglu M, Harraz A, Dimitriadis F, Ceyhan E, Rezano A, Zwamel AH, Ibrahim W, Benabbou A, Margiana R, Gnoneye E, Rabin MMM, Omirinde J, Esmaeili V, Zini A, Arafa M, Elbardisi H, Toprak T, Dursun M, Khalafalla K, Salvio G, Chung E, Crafa A, Shah R, Agarwal A. Sperm DNA Fragmentation in Men with Varicocele: A Systematic Review and Meta-Analysis. World J Mens Health. 2026 Apr;44(2):268-289. doi: 10.5534/wjmh.250025. Epub 2025 Jun 19. PMID: 40583011; PMCID: PMC13036259.

Aboulmaouahib, S., Madkour, A., Kaarouch, I., Sefrioui, O., Saadani, B., Copin, H., Benkhalifa, M., Louanjli, N., & Cadi, R. (2018). Impact of alcohol and cigarette smoking consumption in male fertility potential: Looks at lipid peroxidation, enzymatic antioxidant activities and sperm DNA damage. Andrologia, 50(3), e12926. https://doi.org/10.1111/and.12926

Hoang-Thi AP, Dang-Thi AT, Phan-Van S, Nguyen-Ba T, Truong-Thi PL, Le-Minh T, Nguyen-Vu QH, Nguyen-Thanh T. The Impact of High Ambient Temperature on Human Sperm Parameters: A Meta-Analysis. Iran J Public Health. 2022 Apr;51(4):710-723. doi: 10.18502/ijph.v51i4.9232. PMID: 35936544; PMCID: PMC9288403.